我們寫一個關于系統信號量的程序并用 go run 調試。
測試代碼如下

package mainimport ("os""os/signal""fmt""syscall" )func main() {sig := make(chan os.Signal)signal.Notify(sig, syscall.SIGUSR2)for {select {case s := <-sig:fmt.Println(s.String())}} }

使用 go run main.go 運行程序，并使用ps -ef|grep main.go 找到進程 ID，然后傳遞 USR2 信號。

kill -USR2 [id]
發現程序并沒有任何輸出，其實我們只要知道 go run 命令的原理這兩點就不難理解，go run 命令會編譯 go 源碼為可執行文件并保存到臨時目錄，然后執行可執行文件，所以我們運行的 go run 命令的進程號并不是我們的 go 代碼進程號。
我們可以使用 go run -x main.go 查看 go run 命令執行的一些列命令集合。

$ go run -x main.go
WORK=/var/folders/7l/7jhnyrh96bb75x9ljjt2vyz80000gn/T/go-build415823243
mkdir -p $WORK/b001/
cat >$WORK/b001/importcfg.link << 'EOF' # internal
packagefile command-line-arguments=/Users/liushuai/Library/Caches/go-build/fd/fd82f5fac0921efb6ce9dd7abb086e6324c196d2d4c71186f461975d358cc314-d
packagefile fmt=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/fmt.a
packagefile os=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/os.a
packagefile os/signal=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/os/signal.a
packagefile syscall=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/syscall.a
packagefile runtime=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/runtime.a
packagefile errors=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/errors.a
packagefile io=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/io.a
packagefile math=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/math.a
packagefile reflect=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/reflect.a
packagefile strconv=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/strconv.a
packagefile sync=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/sync.a
packagefile unicode/utf8=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/unicode/utf8.a
packagefile internal/poll=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/internal/poll.a
packagefile internal/syscall/unix=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/internal/syscall/unix.a
packagefile internal/testlog=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/internal/testlog.a
packagefile sync/atomic=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/sync/atomic.a
packagefile time=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/time.a
packagefile internal/race=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/internal/race.a
packagefile internal/bytealg=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/internal/bytealg.a
packagefile internal/cpu=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/internal/cpu.a
packagefile runtime/internal/atomic=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/runtime/internal/atomic.a
packagefile runtime/internal/sys=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/runtime/internal/sys.a
packagefile unicode=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/unicode.a
packagefile math/bits=/usr/local/Cellar/go/1.11/libexec/pkg/darwin_amd64/math/bits.a
EOF
mkdir -p $WORK/b001/exe/
cd .
/usr/local/Cellar/go/1.11/libexec/pkg/tool/darwin_amd64/link -o $WORK/b001/exe/main -importcfg $WORK/b001/importcfg.link -s -w -buildmode=exe -buildid=leDM4Psk9hp9WmZnpLM_/e3zL8UstMmCxJEhM2eG/ogq34jjayAFU3M9ke-dB/leDM4Psk9hp9WmZnpLM?-extld=clang /Users/liushuai/Library/Caches/go-build/fd/fd82f5fac0921efb6ce9dd7abb086e6324c196d2d4c71186f461975d358cc314-d
$WORK/b001/exe/main
第一行的 WORK 變量的值就是臨時執行文件放置目錄的目錄。最后一行 $WORK/b001/exe/main 就是運行臨時目錄文件，我們可以根據 WORK 變量名使用 ps -ef|grep “WORK” 找到我們程序運行的真正進程 id。
我這里找到進程ID方法如下：

$ ps -ef|grep "/var/folders/7l/7jhnyrh96bb75x9ljjt2vyz80000gn/T/go-build415823243"|grep -v grep |awk '{print $2}'
32315
發送 USR2 信號

kill -USR2 32315
可以看到如下輸出

user defined signal 2
使用 -x 未免復雜，我們可以再 go run 后添加一個特定字符串就可以很容易找到了。
比如，我們以下方式啟動

$ go run main.go asdfadsfadsf
查找進程 id

$ ps -ef|grep asdfadsfadsf |grep -v grep [16:19:26]
501 32542 20124 0 4:19下午 ttys011 0:00.21 go run main.go asdfadsfadsf
501 32552 32542 0 4:19下午 ttys011 0:00.00 /var/folders/7l/7jhnyrh96bb75x9ljjt2vyz80000gn/T/go-build688063792/b001/exe/main asdfadsfadsf
第二個進程即我們代碼運行的真正進程。

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